05-8-12 T.Amaya 1

Special Lecture

Socio-Environmental Aspects of Construction materials

Concrete Admixtures

Date & timeAugust 12 13:0014:30

Place Hokkaido University

Presented by Dr.T.Amaya

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Ex. Reports on concrete reported by general contractors-- Big general contractors, i.e.Taisei, Kazima , Obayashi, Shimizu,

Takenaka, have published their own R&D reports.-- Total = 4,224 / Reports on concrete = 776 (19802003)

Fig-1 Number of reports on concrete

0

10

20

30

40

50

1980 1985 1990 1995 2000

(18.4%)

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1. IntroductionMost of presentations & reports on concrete can be classified into :---

Basically important Recently coming Rare case

Raw materialsWorkability as RMC Hardened propertiesStructural aspectsDurabilityFire resistance

etc.

RecyclingWaste problemEnvironmentEcology

Gas emissionSafety aspect

of materialsRisk aspects

Accident

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Abbreviation

RMC Ready mixed concreteAE-WR Air entraining water reducerAE-MRWR Air entraining mid range water reducerAE-HRWR Air entraining high range water reducerHRWR High range water reducerLS LignosulfonateMS MelaminesulfonateSG Sodium gluconatePC Polycarboxylate

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Fig-2Reports on High Strength & High Fllowing Concrete

0

2

4

6

8

10

12

14

1980 1985 1990 1995 2000

Part of New RC Project

R&D from structural points

Over 100N/mm2

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Fig-3Number of reports on concrete durability

01

2

3

45

6

7

8

1980 1985 1990 1995 2000

Studies on concrete-durability have been constantly done to gethigh quality of concrete.Ex. Alkali-silica reaction, Cl- ion migration, freezing & thawing

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Technical fields of reports on concrete

High strength &High flowing Concrete

Durability, eg. alkali-silica, freezing-thawing

Precast concrete& Prestressed

concrete

Environment & Resource, e.g.Recycle, Porous concrete

Machining, e.g. cutting

Specified method, e.g. sprayed concrete, RCD

Construction method, e.g. concreting

Specified additives, e.g.expansion agents,anti-corrosion agent, etc.

Raw Material, e.g.cement, admixture, aggregates

Mechanical property asstructual components

Non-destructive testing

Seismic strengthening

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2 Cement as main raw materials of concrete1) History of cement If concrete is defined to be composite material

of lime based binder and aggregates, Sazare-Ishi would be the oldest concrete.

National anthem

Neolithic era, BC7000, 40 MPa of high strength concrete composed of lime (calcite) and aggregate was used in Israel.

BC300, Rome era, mixture of lime, aggregateand Pozzolana were mixed and cured in molds. Such concrete was widely used for constructionin Roma.

Natural concrete formedBefore 270 million years

ForoRomano (BC2 century)

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Main cause of hardening of these concrete was carbonationof Ca(OH)2.

Beginning of 19 century, hydraulic hardening minerals wereinvented by burning the mixture of lime and silica.In 1824, J.Aspdin invented the basic technology of presentPortland Cement. Its color resembled to the stone in Portland Island.

Naming origin

Industrialization of cement prevailed in the world.Germany in 1850 / America in 1871 / Japan in 1875

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2) Production volume72.4 Mio ton in 2004 Export 10.3 Mio.ton (14%)

Ordinary PC40.5 Mio ton(68.3%)

Blast furnace slug15.1 Mio ton

High early trength PC 2.7 Mio. ton

Other PC 0.6 Mio. ton

Fly-ash 0.4 Mio.ton

68.3%

4.6%

Portland cement 43.8 Mio.ton 73.9%Blended cement 15.5 Mio.ton 26.1%

Cement production

1953

1996

1986 2002

Export

1971

7 Mio.ton

In 2002

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3 Chemical admixtures1) Introduction Before 1960 concrete was mainly produced at job site.

Around 1960 ready mixed concrete was produced byabout 500 RMC plants.

Liability of concrete quality increased / Agitator truck delivery Around 1965 almost all concrete was produced by RMC plants.

Admixtures are materials used for improving properties of concrete &/or mortar.(Powdery) Admixture Improvement can be done by large amount. Chemical admixture Improvement can be done by small amount

JIS A 6204 & Association norms Improvement items are workability, strength development, etc. Chemical admixture has been used to get workability with

decreasing mixing water.

The 1st RMC plant in 1949

13

Admixtures Example of main components Use of purpose

1 Air-Entrainer Nonion type surfactant Workability / Freezing & thawing2 AE Water Reducer Lignosulfonate / Gluconate3 AE-High Range Water Reducer Polycarboxylate4 AE-Mid range water reducer Polycarboxylate / Lignosulfonate

5 High Range Water Reducer Melamine / Polycarboxylate Strenth development / Workability

6 Set retarding water reducer Gluconate7 Set accelerating water reducer Nitrite / Nitrate / Thiocyanate 8 Anti-freezing admixture Nitrite / Nitrate / Thiocyanate 9 Hardening accelerator Calcium chloride

10 Superplasticizer Sulfonated naphthalene Workability / Job-site addition11 Anti-washout admixture Cellulose base & Acrylic acid Underwater concrete

12 Shotcrete accelerator Calcium aluminate Setting time / Hardening time13 Corrosion Inhibitor Nitrite / Aminoalcohol Corrosion14 Shrinkage reducing admixture Copolymer of Alkyleneoxido Surface tension

15 Shrinkage compensation agent CSA Introduce chemical prestress16 Fly ash17 Blast furnace slug powder18 Silica fume19 Calcite powder Workability / Segregation20 Cement polymer emulsion Emulsion of SBR, EVA & Acryl Workability /Durability / Adhesion

Durability / Long term strength

Workability / Higher strength etc.

Chemical admixtures mainly for water reduction

Other chemical admixtures

Powder type admixture

Setting time / Hardening time

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2) General properties of chemical admixtures Chemical admixture is one kind of surfactant to get

-- better workability of RMC -- better durability of hardened concrete

Chemical admixture can :---- reduce water in RMC under the same slump (flow)-- introduce small air-bubble properly-- extend working time of RMC, e.g. slump & flow life

Chemical admixture react cement particles by :---- electrostatic repulsive force -- chelate effect -- steric hindrance

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(a) Slump cone (b) Shape of slump

Sticky concrete Acceptable concrete Material separation

Minutes

AE-WR

AE-MRWR

Slump change with time (27N/mm2-18cm-20mm N)

Slump

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3) History of water reducer Long history

Year Mechanism of effect

1920 Lignosulfonate (LS) By-product of pulp industry Electrostatic repulsion

1931 Sodium Gluconate (SG) Fermentation of glucose Chelate of COO - ion

1965 Sulfonated naphtalene Copolymerized by formaldehyde Electrostatic repulsion

1966 Sulfonated melamine Copolymerized by formaldehyde Electrostatic repulsion

1982 Modified polycarboxylate Meth acrylate copolymer Steric hindrance

1985 Amino sulphonated Aminosulphonate copolymer Steric hindrance

1990 Comb type polycarboxylate Meth acrylate copolymer Steric hindrance

1998 Modified polycarboxylate Polyamido modified aclylate Steric hindrance

Market share of LS based admixture is over 50%. Methacrylate copolymer based admixture is still under development.

Main water reducing admixtures used in concrete industry

Raw materials

Remark Even LS & SG based admixtures are still under improvement, e .g. additives.

Graft of polymer

Cement grain + + + + + + + + + +

The 1st use of admixture in Japan might be in 1932.

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Features of chemical admixture industryCompany of chemical admixture are formulators :---- Almost all raw materials are purchased. -- Even main raw materials are purchased, e.g. LS, SG.

(Own production is rare case.)Chemical admixtures are composed of :--

Formulation confidentiality is very important.Very hard to know chemicals from MSDSAlmost all chemical admixtures are produced by mixing thepurchased raw materials, which enables special product bybatch production. Possible to make Tailor made productTransport costis important for management because of water.

Main raw material Air contents, slump, initial strength, antiseptic

Water

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4) Water reducers(1) Lignosulfonate (LS) based Water Reducer Main use of LS (in 1997 / Solid content base)

105 k ton = Admixture (67k t) + Dye disperser (8k t) +.. Ca, Na, Mg base / High molecular electrolyte / Anion type

Molecular weight of LS : 10,000 or more

Long history, i.e. established technology.Less technical progress now / Mainly Delivery & Marketing But, still mainly used, especially in civil engineering works.In Tokyo area, demands of LS decreases because of aggregate.

Cheapest raw material as admixture raw materials Cement dispersion is done by elect